Next generation mobile communication systems have been standardized aiming at providing integrated services and effective interoperations between a wired communication network and a wireless communication network, beyond a simple wireless communication service provided in the conventional mobile communication systems. With the demand on a high-speed, large-volume data communication system for processing and transmitting a variety of information such as radio data as well as providing voice-oriented services, there is a need for developing a technique for transmitting large-volume data through the wireless communication network whose capacity is similar to that of the wired communication network.
An orthogonal frequency division multiplexing (OFDM) system capable of reducing inter-symbol interference with a low complexity is taken into consideration as one of next generation (after a 3rd generation) systems. In the OFDM system, serial input data symbols are converted into N parallel data symbols and are carried and transmitted on separate N subcarriers. The subcarriers maintain orthogonality in a frequency dimension. Orthogonal channels experience mutually independent frequency selective fading. Inter-symbol interference can be minimized since intervals of transmitted symbols are lengthened. Orthogonal frequency division multiple access (OFDMA) is a multiple access scheme in which multiple access is achieved by independently providing some of available subcarriers to a plurality of users when using a system which employs the OFDM as a modulation scheme. In the OFDMA, frequency resources (i.e., subcarriers) are provided to the respective users, and the respective subcarriers are independently provided to the plurality of users. Thus, the subcarriers generally do not overlap with one another. Eventually, the frequency resources are mutually exclusively allocated to the respective users.
For the effective use of limited radio resources, a base station (BS) schedules the radio resources. When there is no data packet transmitted using radio resources allocated to a user, the BS performs scheduling such that unused radio resources can be used by another user. Thus, the radio resources can be further effectively used. As such, radio resources may not be allocated to a user who does not have a data packet to be transmitted/received. Instead, the radio resources may be allocated to a user who has a data packet to be transmitted/received. In this manner, the radio resources can be dynamically allocated on a frequency domain or a time domain. Such a scheme is referred to as dynamic scheduling.
In a voice over Internet Protocol (VoIP) service, a VoIP packet may not be transmitted. Even in this case, the resources are persistently allocated until a VoIP session is closed. That is, once allocated, the radio resources are maintained for a predetermined time period. Such scheduling is referred to as persistent scheduling, which leads to efficiency deterioration under the limited radio resources.
Accordingly, there is a need for a method for effectively managing limited radio resources in a VoIP service.